- #1
TheRedDevil18
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Homework Statement
The mass of a homogenous thin plate is 36kg. Determine it moment of inertia about the x axis
Homework Equations
Parallel axis theorem:
Ix = Ix' + d^2*m
The Attempt at a Solution
p = m/a
= 36/0.36 = 100
Because the density is homogenous, I found the mass of the first rectangle:
m = pa
= 100*0.24
= 24kg
Ix = Ix' + d^2*m (MOI for the first rectangle)
= 1/12*b*h^3 + d^2*m
= 1/12(0.4)(0.6)^3 + (0.3)^2(24)
= 2.1672
Ix = Ix' + d^2*m (MOI for the second rectangle)
= 1/12*b*h^3 + d^2*m
= 1/12(0.4)(0.3)^3 + (0.15)^2(12).....Mass of second rectangle = 36-24 = 12
= 0.27
Therefore MOI of the whole object = (MOI for the first rectangle) + (MOI for the second rectangle)
= 2.44
Problem is my textbook gives a total different answer which is 3.24. Please help, I am so confused